Running the following program in DrRacket 5.1.1 highlights the `error'
expression if debugging is enabled:
#lang racket
(syntax-case 'a ()
(_ (error 'boom)))
Running the same program in 4d7584d/g doesn't highlight anything.
Without the `syntax-case' around it, both versions highlight the
`error' expression.
Is this a bug? If not, is there a reliable way to associate a source
location with a runtime error?